1. Field of the Invention
The present invention relates to a photographic printer using a laser scanning unit as an exposing apparatus for exposing a sensitized surface of a photographic paper.
2. Description of the Related Art
In recent years, a photographic printer using a laser scanning unit for exposing a latent image on a sensitized surface of a photographic paper is realized. In such the photographic printer, an image data taken by a digital camera or a scanner is used for exposing the latent image without using any film. For example, intensities of three laser beams of red, green and blue emitted from laser light sources are modulated corresponding to gradations of the image data. The modulated laser beams are scanned on the same scanning line on a sensitized surface of a photographic paper by the laser scanning unit. The photographic paper is conveyed in a direction perpendicular to the scanning line of the laser beams, so that the latent image corresponding to the image data is exposed on the sensitized surface of the photographic paper. When the photographic paper is developed, a visual image corresponding to the image data is formed on the photographic paper.
As conventionally known, each photographic paper has an inherent sensitivity, and the sensitivity of the photographic paper is varied corresponding to a condition such as a kind and deterioration of a developer. Thus, it is necessary to adjust the intensities of the laser beams corresponding to the combination of the sensitivity of the photographic paper and the condition of the developer.
The conventional photographic printer has a plurality of lookup tables corresponding to the combinations of the kinds of the photographic papers and the kinds of the developers. Each lookup includes a plurality of data corresponding to the relations between the gradations in the image data and the intensities of the laser beams. The data in the lookup table are referred to control the intensities of the laser beams so as to adjust the density of the visual image on the photographic paper at the same level with no relation to the kind of the photographic paper and the kind of the developer when the same image data is used. The data in the lookup table is called xe2x80x9coptical modulation dataxe2x80x9d in the following description.
FIG. 14 shows an example of a xcex3-characteristic of a specific photographic paper developed by a specific developer. In FIG. 14, the abscissa designates a gradation of the image data having 4096 stages (0 to 4095) and the ordinate designates the density of the printed visual image actually exposed and developed by the photographic printer. Hereupon, it is assumed that the actual sensitivity of the photographic paper used in the photographic printing is higher than the nominal value of the sensitivity of the photographic paper. In such a case, even when the photographic paper is exposed by a laser beam having an intensity by which a density of the developed photographic paper is essentially to be 2.2, the actual density of the developed photographic paper will be 2.5 which is saturated. In other words, even when the intensity of the laser beam is controlled corresponding to the gradation of the image data, the density of the visual image on the photographic paper corresponding to the region between the point P1 and 4095 in the gradation will be saturated. Alternatively, when the actual sensitivity of the photographic paper used in the photographic printing is lower than the nominal value of the sensitivity of the photographic paper, a portion of the photographic paper exposed by the laser beam having the intensity corresponding to the density 2.5 does not satisfy the predetermined density. Thus, the gradation of the visual image on the photographic paper formed by the conventional photographic printer becomes rough, and the quality of the visual image becomes poor.
An object of the present invention is to provide a photographic printer using a laser scanning unit in which the intensities of laser beams used for exposing a photographic paper can be adjusted corresponding to variation of the actual sensitivity of the photographic paper with respect to a nominal value of the sensitivity thereof.
A photographic printer in accordance with the present invention comprises at least one laser light source for emitting a laser beam having a predetermined wavelength, an optical modulator for modulating the intensity of the laser beam emitted from the laser light source by using optical modulation data corresponding to an image data and a scanning mechanism for scanning the laser beam on a sensitized surface of a photographic paper. An intensity of the laser beam scanning on the photographic paper is adjusted corresponding to a combination of an actual sensitivity of the photographic paper and deterioration of a developer with respect to nominal values of them by selecting at least one of controlling a power of the laser light source, compensating the optical modulation data and providing an adjuster for adjusting transmittance of the laser beam when the laser beam passes therethrough on an optical path between the laser light source and the scanning mechanism.
By such a configuration, the sensitized surface of the photographic paper is exposed by the laser beam having a proper intensity with respect to the actual sensitivity of the photographic paper and the deterioration of the developer. Thus, gradation of a visual image formed on the photographic paper (or a photographic print) can be reproduces properly with no saturation. The quality of the photographic print can be increased.